2010 Justa: N12 is supposed to have 63.9 mm slack when new.


At 30K miles, mine measured 65.54 mm.


At 50K miles, it just measured 65.8 mm. Original tensioner has NOT been replaced.


Oil/filter changed every 5K miles with Mobil 1 0W-40 (a little thinner when cold than Mini/Castrol oil, pumps up tensioner a little quicker).


If the wear rate is linear, I should be just under 68 mm in 150K miles. (This will probably require the "long" tensioner at that point or an entire replacement of the TC assembly.)


Hope this helps Justa owners to gauge their wear rates and have a benchmark to apply. I strongly suggest getting at least a couple measurements of your car so you can determine what your wear rate appears to be.


DOC

 

Can you post details of how to measure?

 

You need the special tool that replaces the tensioner or have a dealer or shop do it.


DOC

 

Ugh. Bummer, that. I'll have to look into that. Perhaps after my warranty is up.

 

I would suggest having your dealer do it now to establish a baseline and then again just before your warranty expires. That way, you can potentially get a new timing chain assembly without paying $2400 (dealer price) for it. (Justas are not part of the "program" that is for N14 motors.)


If they charge more than an hour of labor, they are hosing you. (Herb Chambers in Boston did it twice for me at no charge.)


DOC

 

DOC,
I'm following your idea of measuring my N12 timing chain slack. I'll be paying 'Retail', probably. Do you believe one shop hour would do it? It will be at a MINI dealership in Michigan.

 

1 hr should be fine for a measurement

DOC, where did you get the 63.9mm as the baseline spec?

 

Well, a few months later, I have had my timing chain slack measured for about $300. I believe it was worth it. My slack was 69 mm, or 1 mm beyond the tolerance zone. The tensioner bolt was not working correctly either with too much movement and too easily moveable (he demonstrated the dampening with a thumb on the bolt.) The bolt was replaced as part of the operation.
Mine is a 2008 production N12 with 65,000 miles, always bathed fully in the best of clean oils, so it couldn't have had a better chance for a normal life, but it fell victim to the design flaw to this extent. The dealership has only measured two or three of the N12 chains in all this time.
I feel better going into the future now knowing that I've given this engine a better chance at a long life.

 

I saw your other post first and replied to that, so please take a look and reply. At a Mini dealer, $300 is about what it costs for labor to measure and full retail to install a new tensioner.

If you found that your tensioner compressed very easily in your hand for the initial travel, you did need a new one. If you got the "long" one, I think you will be OK for about another 20-25K miles, starting out with 69 mm of slack.

However, yours seems to be wearing at a much faster rate than mine, so I would budget for a full TC system replacement before 90K miles. An independent Mini shop in my area charges about $1200 for that.

DOC

 

DOC4444, I'll find the other post-and-reply too, thanks for your input on the situation. It's a bit depressing to set aside that $1200 or more, but it seems that I'd better do that. It's good to have a place to discuss this. I wonder which forum thread is the best one for on-going discussion?

 

N16 here, still under factory warranty. Is this a check they'll do under the 4 yr maint plan?

 

kyoo,
I seriously doubt that MINI would do much of anything even for an N12, much less an N16, in any official sense. Perhaps on an N14 under warranty in which they would have to pay the repair. It would be nice to ask just to see MINI's attitude toward the N16 chain condition. Let us know if you do find out anything.

 

true true. it's only 10mo 8k miles right now though, so it'll probably ahve to wait but I'll keep everyone posted as time goes on

 

Well, I am at 65K, miles now. I just had the slack measured again at the same dealer (Herb Chambers, Boston, MA). It was the same shop as previously, but a different tech. He got 65.2 mm, this time.

Seems odd, because it is LESS than at 50K. One would expect at least a small increase, over time. So, I will put it down to the vagaries of a different person using the measuring tools. (No parts were replaced, except the gasket. OEM tensioner is STILL installed.)

I now have three data points that suggest it will quite a while before 68 mm is reached.

BTW, Mark Ravin (service writer) and Casey (tech) have been FANTASTIC with addressing the niggling problems the car has had along the way.

DOC

 

We offer the tensioner test tool on our we site for approx. $25.00 In all honesty i would not spend too much money on having chain length tested. I would invest that money on doing the chain project. We have done that project in our service shop many times. And once done complete, with new chain, tensioner rails, etc. We have never had an issue with that car again.

here is the link to the tool item # 138018

 

curious, i still haven't heard of any failures for the non-s Coopers - especially the newer (2011+) ones

 

Blue, you really shot you and your company in tbe foot with that post! So, following your advice people should not "waste money" on periodically checking their timing chain slack until they, what, need a new motor?

I have been acquiring data, admittedly for my benefit, that literally is not available anywhere else and providing it to this community. So, if people have 2007-2010 Justas and they change their oil every 5000 miles like I do, now it is starting to look like they can expect to get to at least 100K miles before they hit 68 mm.

There HAVE been several reported valve/piston meetings on this forum with early 2nd Gen Justas (probably due to stuck tensioners caused by low oil levels and grit in the oil from those 15K oil change intervals, but who knows for sure).

Based on my data, I still would check at least once around 50 to 60K, just to make sure the pattern of wear is following mine. (Like a poster in this thread did and found he was over the limit.)

Or, they can follow your advice and wait to do the timing chain when they need a new motor.

DOC